GB1592139A - Electric circuit breaker - Google Patents

Description

PATENT SPECIFICATION

( 11) ( 21) Application No 18344 i 78 ( 22) Filed 8 May 1978 ( 19) ( 31) Convention Application No 2721 162 ó ( 32) Filed 11 May 1977 in ( 33) Fed Rep of Germany (DE) C 1 ( 44) Complete Specification published 1 July 1981 ij'1 ( 51) INT CL 3 H Ol H 73/22 _i ( 52) Index at acceptance H 1 N 175 181 183 187 191 201 214 241 548 623 700 704 744 ( 72) Inventor FRITZ KRASSER ( 54) IMPROVED ELECTRIC CIRCUIT BREAKER ( 71) We, ELLENBERGER & POENSGEN Gmb H, a German Body Corporate, of Industriestr 2-8, 8503 Altdorf, West Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and

by the following statement:-

The present invention relates to a circuit breaker of the type including a contact spring having a fixed end clamped into a switch housing and a free end provided with a movable contact which is arranged to co-operate with a fixed contact, the spring being biased to urge the movable contact away from the fixed contact, as well as a switching rocker which acts on the spring and a release device responsive to a current overload.

In such a circuit breaker, the rocker is arranged selectively to move the spring into a contact closing position and is mounted in the breaker housing to be pivoted about an axis extending approximately perpendicular to the spring for movement between a breaker opening position and a breaking closing position The release device acts to permit the spring to execute a contact opening movement independently of the position of the rocker.

In such switches, switching off should take place automatically, in dependence on the occurrence of an excess current, even if the switching rocker is being retained in its switch closing position, a trip-free release should be effected.

According to the present invention there is provided a circuit breaker comprising a contact spring fixed at one end, carrying a movable contact at its free end, and biased to urge the movable contact away from an associated fixed contact; a switching rocker pivotally mounted for movement between a breaker closing position in which it can act on the contact spring to urge the movable contact towards the fixed contact and a breaker opening position in which the rocker permits the contact spring to move the movable contact away from the fixed contact, the switching rocker being mounted to pivot about an axis which extends approximately perpendicularly to the length of the contact spring and being provided with means applying a resetting force to the rocker for urging it into its breaker opening position; a housing containing the contact spring and the switching rocker; a latching lever extending approximately parallel, and adjacent, to said contact spring and mounted to be movable in the housing between a contact closing position and at least one contact opening position, said latching lever having a contact end which faces said free end of said contact spring and which is mounted to be displaceable in approximately the direction of switch opening movement of said movable contact, and having a detent end, which is opposite said contact end, said latching lever bearing against said contact spring in a manner to apply thereto a force which is counter to the direction in which said spring is biased; and a release device within the housing arranged to be responsive to a current overload and operative to permit the contact spring to move the movable contact away from the fixed contact upon the occurrence of a current overload irrespective of the position of the, switching rocker; said release device comprising a detent abutment movable between a detent position in which it is engageable with the detent end of the latching lever and a release position in which it is removed from the path of movement of said detent end; said switching rocker being disposed to that side of the latching lever which is remote from the contact spring; and said switching rocker including an active end which protrudes toward the latching lever and which lies, when said rocker is in each of its positions, at a respectively different side of a line extending approximately perpendicular to the length of the latching lever and passing through the pivot axis of the rocker, said active end being operatively associated with the latching lever for moving the latching lever into its contact closing position when the rocker is in its 1592139 1,592,139 breaker closing position and the detent end of said latching lever is in engagement with the detent abutment.

The circuit breaker can be made with a relatively compact structure, with its main components essentially disposed one above the other in the pivot plane of the switching rocker The pivot axes can all be perpendicular to the pivot plane of the switching rocker, this facilitating installation of the circuit breaker.

In a preferred embodiment of the invention, the active end of the rocker rests, in the closing position of the rocker, in a first detent recess provided in the latching lever, so that the switching rocker, whose active end produces the contact pressure when it is in the closing position, will not inadvertently be changed from that position to the opening position, for example by the counter pressure of the contact spring This feature is of significance particularly when the rocker is under the influence of a resetting force which urges it into its breaker opening position.

Preferably, the latching lever presents a cam path which includes the first detent recess and along which the active end of the switching rocker travels when moving between its positions, the cam path having a projection located in the vicinity of the centre dead point of the active end and protruding toward the switching rocker axis, and the cam path including a second detent recess in which the active end of the rocker rests, in the opening position of the rocker, and which is located at a greater distance than the first recess from the rocker axis.

This ensures that the active end of the switching rocker, when the rocker is in its opening positions, is unable to exert any contact pressure on the contact spring via the latching lever.

Preferably, in the above-mentioned embodiment, the active end of the rocker effectively terminates in a laterally protruding guide projection which rests on the cam path, and the cam path is defined by a guide groove which is closed on all sides and which guides the projection This has the result that transfer of the switching rocker from the closing position to the opening position raises the detent end of the latching lever so that the patent abutment can return unimpededly to its respective starting position.

The release device may conveniently include a release lever which also provides the abutment and which is subjected to a resetting force which urges it in the direction opposite to that required to release the spring so as to bring the abutment into position to engage the latching lever This permits automatic return of the detent abutment into its starting position once the element responsive to a current overload, e.g a bimetal strip has cooled and as soon as the detent end of the latching lever has been raised.

The release lever suitably may be an 70 angular, or bell crank, lever one arm of which is acted on by the overload responsive element and extends approximately parallel to the contact spring and/or the latching lever, so that the release lever pivots 75 in the same plane as the switching rocker.

Favourable lever ratios are achieved when the one arm of the release lever is approximately of the same length as the contact spring and/or the latching lever, and a 80 simple structure effecting automatic return of the detent abutment into its starting position, when the detent end of the latching lever is raised and the overload responsive element has cooled, is provided when the 85 other arm of the angular release lever extends approximately parallel to lateral housing walls and the resetting force for the release lever is provided by a spring interposed between that other arm and such 90 lateral wall.

The active end of the switching rocker can be constituted by two parallel arms which fit snugly around the latching lever and which form a bearing for the guide 95 projection, and the guide projection is in the form of a pin or axle This enables the bitmetal strip constituting the overload responsive element, and its pivot plane, to also be located in the pivot plane of the 100 switching rocker which favours compact design and makes the switch particularly suitable for use in a row of such switches in major switching systems This structural arrangement also improves stabilization of 105 the guidance of the latching lever in the switch housing.

In further accordance with preferred embodiments of the invention, in which the active end of the switching rocker effectively 110 terminates in a laterally protruding guide projection which rests on the cam path, and the cam path is defined by a guide groove which is closed on all sides and which guides the projection, a resetting force is applied to 115 the switching rocker to urge it into its breaker opening position, the portion of the cam path of the latching lever between its centre dead point projection and the path end associated with the closing position is 120 sloped in such a way that when the detent abutment is moved away from the detent end of the latching lever, that cam path portion extends approximately in the direction of the arc of travel of the active end 125 of the switching rocker, thereby nullifying the detent action which acts on the rocker when in its breaker closing position This produces automatic raising of the detent end of the latching lever after a trip-free release, 130 1,592,139 unless the switching rocker is externally blocked in its breaker closing position.

When the structure is further arranged to subject the release lever to a resetting force which opposes the release force produced by operation of the overload responsive element and which moves the release lever into a position where the detent abutment can engage the detent end of the latching lever, and so that the release lever has the form of an angular lever having an arm extending approximately parallel to a lateral housing wall, and so that the resetting force is generated by a spring interposed between that arm and that wall, the resulting arrangement has the capability of automatically reestablishing the starting state of the breaker switch for renewed switch-on after a tripfree release has occurred and the bimetal strip has cooled.

A particularly advantageous embodiment of the invention has the form of a two-pole circuit breaker composed of two juxtaposed single-pole switches and operating in the same manner as the above-described singlepole circuit breaker switches but being distinguished by the fact that only a single one of certain significant actuation members, such as the switching rocker, the latching lever and the detent abutment, are provided but are equally effective for both single-pole switches.

The invention will be further discribed, by way of example, with reference to the accompanying drawings:

BRIEF DESCRIPTION OF THE

DRAWINGS Figure 1 is a function and kinematic linkage diagram of a single-pole circuit breaker switch according to the invention in the switched-on, or contact closing, position.

Figure 2 is a view similar to that of Figure with the breaker in its contact opening, or switched-off, position after a trip-free release, and with the switching rocker in its breaker closing position.

Figure 3 is a view similar to that of Figures 1 and 2 after switch-off and with the switching rocker in its breaker opening position, the state shown in Figure 3 existing if switch-off occurs by way of pivoting the switching rocker or by trip-free release as a result of a current overload.

Figure 4 is an elevational, cross-sectional side view of a preferred embodiment of a two-pole circuit breaker switch, according to the invention, combined of two singlepole switches operating generally as shown in Figures 1-3 and in the operating state shown in Figure 1.

Figure 5 is a cross-sectional view along the line V-V of Figure 4.

Figure 6 is a cross-sectional view similar to that of Figure 4 with the switch in its contact opening, or switched-off position, where switch-off occurred as a result of a current overload, the switching rocker is in its breaker opening position, and at least one bimetal strip not yet cooled.

Figure 7 is a view similar to that of Figures 4 and 6 after actuation due to a current overload, i e trip-free release, and with the rocker in its breaker closing position.

Figure 8 is an exploded perspective view of the components of the two-pole circuit breaker switch shown in Figures 4-7.

DESCRIPTION OF THE PREFERRED

EMBODIMENTS Initially the structure and operation of a single-pole circuit breaker switch according to the invention will be described and ex 85 plained with the express mention that the structure and operation of this single-pole switch essentially coincide with the structure and operation of the two single-pole switches of the embodiment according to Figures 90 4-8.

Referring thus to Figures 1-3, within housing 1 whose pertinent wall portions are indicated by hatching in Figures 1-3, a contact spring 2 is fixed via its end 3 to a 95 connecting lug 4 which is permanently secured to the housing wall At its free end 5, the contact spring 2 carries a movable contact 6 which coacts with a fixed countercontact 7 fastened to a contact lug 8 which 100 is likewise permanently connected to the wall of housing 1 Contacts 6 and 7 constitute the switching point in the circuit to be protected The contact spring 2 is -stressed, or biassed, in the contact breaking 105 direction 9, to enable it to automatically break the connection between contacts 6 and 7.

Above the contact spring 2, a switching rocker 10 for manually operating the breaker 1-10 is arranged to be pivotal about an axis 11 extending at a right angle to the length of contact spring 2 The axis 11 is fixed in housing 1.

Between contact spring 2 and a switching 115 rocker 10, there is provided a latching lever 12 which extends approximately parallel to the length of contact spring 2 The latching lever 12 is mounted within housing 1 to be pivotal in the pivot plane of the switching 120 rocker 10 and has a contact end 13 which is adjacent the free end 5 of the contact spring and is displaceable approximately in the contact breaking direction 9 For this purpose, there is provided in housing 1 a 125 longitudinal guide 14 for guiding the contact end 13 of latching lever 12.

The latching lever 12 bears against the back of contact spring 2 near the area of contact 6 via an arm 15 which is connected 130 1,592,139 to the latching lever 12 Thus any force exerted on spring 2 by lever 12 is in opposition to contact opening direction 9.

The end 16 of the latching lever 12 which is opposite the contact end 13, end 16 hereinafter being called the detent end, is arranged to rest, when the switch is in the state shown in Figure 1, on a detent abutment 17 which is disposed, as is contact spring 2 below the latching lever 12 Detent abutment 17 is mounted in housing 1 to be pivotal about an axis 18 which is parallel to axis 11 Abutment 17 is formed at the end of an arm 37, hereinafter called the load arm, of an angular, or bell crank, lever whose other arm, or power arm, 19 is subject to the switch opening force produced in direction 20 by a current overload responsive element, which will be described in detail below The lever 35, and particularly detent abutment 17, is under the influence of a resetting spring 21 supported at the wall of housing 1 and acting in opposition to the pivoting direction 20 Spring 21 is shown schematically as a compression spring, but can be constituted by another spring type, such as a torsion spring.

While the contact spring 2 and the detent abutment 17 act from the bottom substantially on respective opposite ends of the latching lever 12, the switching rocker 10 acts from the top on approximately the center of latching lever 12 This action takes place via the active end 22 of the switching rocker 10, which end extends radially from, or below, the axis 11.

A line 23 -perpendicular to latching lever 12, i e perpendicular to the connecting line between contact end 13 and detent end 16, when lever 12 is in the position shown in Figure 1, passes through axis 11 When rocker 10 is in its breaker closing position, shown in Figures 1 and 2, the active end 22 is disposed to the right of line 23, and when rocker 10 is in its breaker opening position, shown in Figure 3, end 22 lies to the left of line 23 When the breaker is in its switchedon state, in which the detent end 16 of the latching lever 12 rests on the detent abutment 17 and is supported thereby, as shown in Figure 1, end 22 presses the latching lever 12 into the position in which it acts on contact spring 2 to press contact 6 firmly against contact 7 The closing pressure for the contact spring 2 is thus produced by the active end 22 of the switching rocker 10 and is transferred via the contact end 13 of the latching lever 12.

Latching lever 12 presents a cam past 25 along which a lateral guide protrusion 28 fixed to active end 22 is guided Cam path presents two detent recesses 24 and 27 and a projection 26 directed toward axis 11 and located between recesses 24 and 27.

When the switch is in the switched-on, or contact closing, state shown in Figure 1, protrusion 28 of the active end 22 of the switching rocker 10 rests in detent recess 24 Recess 24 is thus associated with the breaker closing position of rocker 10 During 70 pivoting of the switching rocker to its breaker opening position, protrusion 28 of the switching rocker moves along cam path 25, past projection 26, into recess 27 Projection 26, which projects toward the axis 11 75 of the switching rocker, is located at the center dead point position of the active end 22, i e approximately at the level of the line 23 The recess 27 in the cam path 25 is associated with the breaker opening posi 80 tion of the switching rocker, faces the detent end 16 of lever 12, and terminates at a greater distance from the axis 11 of the switching rocker than does the detent recess 24 85 In the practical embodiment shown in Figures 4-7, the lateral guide protrusion 28 is constituted by a pin 39 engaging in a guide groove 29 which is closed on all sides and defines the cam path 25 The guide 90 groove 29 has a generally V shape and the peak 30 of the V, corresponding to projection 26, points toward the switching rocker The branch 31 of the V (Figure 8), which corresponds to detent recess 27, and 95 which extends toward the detent end 16 of the latching lever 12, is longer than the branch 32 (Figure 8) of the V which corresponds to recess 24 and which extends toward the contact end 13 of lever 12 100 The switching rocker 10 is under the influence of a resetting force which urges it in the direction of the arrow 33 of Figures 1-3 and is produced by a torsion spring 34 shown in Figures 4-8 105 The power arm 19 of angular lever 35, which is acted on by bimetal strips 36 constituting overload responsive elements, extends approximately parallel to the contact spring 2 and/or to the latching lever 12 The 110 power arm 19 has approximately the length of contact spring 2 and/or of the latching lever 12.

The load arm 37 of the angular lever 35 extends approximately parallel an adjacent 115 lateral wall of housing 1 The resetting force acting on the load arm 37 in opposition to the pivoting direction 20 is produced by the resetting spring 21 disposed effectively between the load arm 37 and the wall of 120 housing 1.

The active end 22 of the switching rocker is constituted by two parallel arms 38 which surround the latching lever 12 while resting against its sides and thus guiding it 125 Arms 38 form a mount for the pin, or axle, 39, corresponding to guide protrusion 28.

Pin 39 engages in' the guide groove 29 of the latching lever 12.

The two-pole switch embodiment illus 130 1,592,139 trated in Figures 4-8 is distinguished by the particularity that the latching lever 12 and the angular lever 35 are disposed between two single-pole circuit breaker switches 41 and 42 provided in housing 1 The latching lever 12 and the angular lever 35 are disposed in a chamber 44 which is separated by housing partitions 43 from switching chambers 45 and 46 of the two single-pole switches The latching lever 12 contacts the back of both contact springs 2 of the switches by means of a pin, or shaft, 47 which projects on both sides into chambers and 46 in the area of its contact end 13.

This bidirectionally protruding pin 47 extends through the contact end 13 of the latching lever 12 and extends parallel to the axis 11 of the switching rocker This pin 47 is made of electrical insulating material.

After the device has been assembled, pin 39 is trapped between partitions 43 so that it is positively prevented from sliding out of place.

The power arm 19 of the angular lever 35 is provided at its free end with bidirectionally projecting protrusions 48 which extend into the path of displacement of respective bimetal strips 36 associated with the single-pole switches.

The pin 47 has its end guided in longitudinal grooves 49 and 50 formed in lateral walls of housing 1 and constituting the longitudinal guides 14 In the area of the longitudinal grooves 49, 50 the housing walls are covered by covering walls 51 and 52, made in particular of insulating material so that longitudinal displacement of the pin 47 inserted in housing 1 in its axial direction is prevented Walls 51 and 52 are covered by cover plates 56 provided with tabs 57 that can hold housing 1 in a breaker panel The covering walls 51 and 52 and plates 56 are fastened to housing 1 by means of a tubular rivet 53 which is pushed through a hollow shaft 54 forming the pivot bearing of the switching rocker 10 and which is supported in bores 55 formed in the lateral walls of the housing 1.

The connecting lugs 4 project out of the housing and are secured tightly in housing 1 by being twisted Each bimetal strip 36 is of U-shaped design and is fastened to a respective connecting lug 4 via the end of one of its arms 59 while the end of the other arm 60 of the U is angled and permanently conductively connected with a bimetal strip lead 64 that ends in a connecting lug 61 which is also fixed in the wall of housing 1 by twisting.

The fixed end 3 of each contact spring 2 is welded to a connecting lug 4 to form a conductive connection therewith Each fixed contact 7 is permanently connected to a contact terminal 62 which forms a one-piece unit with a connecting lug 63 which is' likewise fastened in the wall of housing 1 by twisting.

In the two-pole switch embodiment, the bimetal strips 36 are matched in such a manner that deflection of one bimetal strip 70 in response to a current overload is sufficient to pivot the angular lever 35 in direction and thus open both switch poles If both bimetal strips are being deflected, the release time will be shorter by about 10 % 75 At the lead 64 to each bitmetal terminal 61 there is provided an adjustment screw which itself presses against the bimetal strip via an insulating member 66 Adjustment of screw 65 varies the bias of the 80 bimetal strip and thus influences the release time of the device.

Pin 47, which transfers the contact pressure from the latching lever 12 to the contact springs 2, lies against each spring 2 85 in the region between its associated contact 6 and fixed end 3 since, during switch-off of the switch by movement of the switching rocker, the guide protrusion, or pin, 39 of the active end 22 of the switching rocker 90 passes over the projection 30 defining the peak of the cam path and thus produces an additional pressure which acts on the latching lever 12 in opposition to the opening direction 9 and which causes the contact 95 spring 2 to snap through.

When the circuit breaker of Figures 4-8 is plugged into a breaker panel or other electrical power installation, each current path to be protected is connected in series, 100 or completed, between the lugs 61 and 63 of a respective switching pole Thus, current flows via a lug 61, lead 64, strip 36, contact spring 2, contacts 6 and 7, lead 62 and lug 63., An auxiliary current path is formed 105 between the lugs 4 and 63 via end 3, contact spring 2 and contacts 6 and 7 This auxiliary path is not protected by itself but is controlled by the movement of the strip 36, i e.

by the protected main current path For 110 instance the protected main current path feeds an electric motor while the auxiliary current path feeds its ventilator or a valve etc.

The circuit breaker switch shown in 115 Figures 4-8 operates as follows:With the switch poles initially closed, as shown in Figures 4 and 5, the occurrence of a current overload causes the bimetal strip 36 to bend upwardly and, after coming 120 to abut agains t an associated projection 48 of lever 35 to pivot that lever in the pivoting direction 20 Thus the detent abutment 17 is pivoted away from underneath the detent end 16 of the latching lever 12 which 125 now no longer has a support Thus the detent end 16 of the latching lever 12 can move downwardly Since the prestressed contact spring 2 permanently presses upwardly in the contact opening direction 9 130 1,592,139 against the contact end 13 of latching lever 12, end 13 being guided within longitudinal grooves 49 and 50, the latching lever 12 pivots counter-clockwise about the guide pin 39 acting as a fulcrum The switch is then in the state shown in Figures 2 and 7.

This pivoting of lever 12 decreases the slope of the portion of the latching lever cam path between its projection 30 and the end of detent recess 24 or 32, this portion is oriented so that approximately in the direction of the arc of pivotal movement of guide protrusion 28 or pin 39 of the active end 22 of the switching rocker 10 from its breaker closing to its breaker opening position Thus the detent recess 24, 32 loses its detent function It no longer prevents the switching rocker 10 from pivoting in the direction of arrow 33 of Figures 1-3 back into its breaker opening position, shown in Figures 3 and 6, under the influence of torsion spring 34.

Once the guide pin 39 has been guided, in guide groove 29 past projection 30, into detent recess 27, 31, its continued movement simultaneously produces raising of the detent end 16 of the latching lever 12 into its starting position, above abutment 17.

Then, after the associated bimetal strip 36 has cooled, the resetting spring 21 pivots angular level 35 back into its starting position, shown in Figures 1, 3 and 4, so that abutment 17 again comes to lie below the detent end 16 of the latching lever 12.

To reset the breaker, it is then only necessary to move rocker 10, manually, back into its breaker closing position by application of a force in the direction 40, shown in Figures 2 and 7.

If the switching rocker 10 were held in its breaker closing position during a current overload release, as depicted in Figure 2 by a force in the direction 40, this will not impede the circuit breaker from switching off, i e, it will effect a trip-free release The switching rocker 10 is in that case merely prevented from automatically moving from breaker closing position to its breaker opening position, and thus from raising the detent end 16 of the latching lever 12 to its starting position Of course, rocker 10 must be moved to its breaker opening position before the breaker can be reset.

To the extent that structural features serving to simplify manufacture have been described in connection with the embodiment relating to a two-pole circuit breaker, they can be used analogously as well for a single-pole, circuit embodiment without departing from the scope of the invention.

The combination of the switching members to effect common release of two separateswitches can also be used independently of the structural features of the single-pole switches within the framework of the invention.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

Claims (19)

WHAT WE CLAIM IS: -

1 A circuit breaker comprising a con 75 tact spring fixed at one end, carrying a movable contact at its free end, and biased to urge the movable contact away from an associated fixed contact; a switching rocker pivotally mounted 80 for movement between a breaker closing position in which it can act on the contact spring to urge the movable contact towards the fixed contact and a breaker opening position in which the rocker permits the con 85 tact spring to move the movable contact away from the fixed contact, the switching rocker being mounted to pivot about an axis which extends approximately perpendicularly to the length of the contact spring and being 90 provided with means applying a resetting force to the rocker for urging it into its breaker opening position; a housing containing the contact spring and the switching rocker; a latching lever extending approxi 95 mately parallel, and adjacent, to said contact spring and mounted to be movable in the housing between a contact closing position and at least one contact opening position, said latching lever having a contact end 100 which faces said free end of said contact spring and which is mounted to be displaceable in approximately the direction of switch opening movement of said movable contact, and having a detent end, which is 105 opposite said contact end, said latching lever bearing against said contact spring in a manner to apply thereto a force which is counter to the direction in which said spring is biased; and a release device within the 110 housing arranged to be responsive to a current overload and operative to permit the contact spring to move the movable contact away from the fixed contact upon the occurence of a current overload irrespective of the 115 position of the switching rocker; said release device comprising a detent abutment movable between a detent position in which it is engageable with the detent end of the latching lever and a release position in which 120 it is removed from the path of movement of said detent end; said switching rocker being disposed to that side of the latching lever which is remote from the contact spring; and said switching rocker including 125 an active end which protrudes toward the latching lever and which lies, when said rocker is in each of its positions, at a respectively different side of a line extending 1,592,139 approximately perpendicular to the length of the latching lever and passing through the pivot axis of the rocker, said active end being operatively associated with the latching lever for moving the latching lever into its contact closing position when the rocker is in its breaker closing position and the detent end of said latching lever is in engagement with the detent abutment.

2 A circuit breaker as claimed in claim 1, wherein the latching lever includes means defining a cam path having at least a first detent recess and said active end of the rocker includes means movable along said cam path to engage in said first detent recess when said rocker is in its breaker closing position.

3 A circuit breaker as claimed in claim wherein said cam path further has a second detent recess engaged by said means at the active end of the rocker when the rocker is in its breaker opening position and a projection located between the recesses and projecting toward the rocker axis, said projection defining the centre dead point of the path of pivotal movement of the rocker between its two positions and the second recess extending further from the rocker axis than the first recess.

4 A circuit breaker as claimed in claim 3, wherein said means at the active end of the rocker comprise a guide member protruding laterally from said active end, said cam path being provided by a guide groove formed in the latching lever and closed on all sides in order to retain the guide member.

A circuit breaker as claimed in claim 4, wherein said guide groove has a V-shaped form, with each detent recess being in a respective side, and the projection constituting the apex of the V-shape, that side of the V-shape which faces the detent end of the latching lever being longer than the side of the V-shape which faces the contact end of the latching lever.

6 A circuit breaker as defined in claim 4 or 5, wherein said active end of the switching rocker comprises two parallel arms closely enclosing the latching lever and supporting the guide member.

7 A circuit breaker as claimed in claim 2, wherein said cam path has a projection which projects toward the rocker axis, is spaced from the first detent recess, and is located between the ends of the cam path, and the portion of said cam path between said first detent recess and said projection is sloped in such a manner that when said detent abutment is in its release position, 60 that portion of said cam path extends approximately along the arc of travel of said means at said active end of said rocker, thereby removing any detent action on said rocker when it is in its breaker closing position and said detent abutment is in its release 65 position.

8 A circuit breaker as claimed in any preceding claim, wherein the release device comprises a release lever which is pivotal about an axis parallel to the rocker axis 70 and which has said detent abutment formed at one of its ends; and a bimetal strip arranged to pivot said lever in a direction to move the abutment into its release position upon occurrence of a current overload 75

9 A circuit breaker as claimed in claim 8, wherein said release device further comprises means applying to the lever a restoring force urging said lever in a direction to bring the detent abutment into its detent 80 position.

A circuit breaker as claimed in claim 9, wherein the release lever is an angular lever having two arms, one arm carrying the detent abutment and the other arm being 85 disposed to be acted upon by the bimetal strip and extending approximately parallel to at least one of the contact spring and the latching lever.

11 A circuit breaker as claimed in claim 90 10, wherein said other arm of the angular lever has approximately the same length as at least one of the contact spring and the latching lever.

12 A circuit breaker as claimed in claim 95 or 11, wherein said one arm of the angular lever extends approximately parallel to a lateral wall of the housing and the means applying a restoring force comprise a restoring spring interposed between said one 100 arm of the angular lever and the lateral housing wall.

13 A circuit breaker as claimed in claim 10, 11 or 12, wherein said bimetal strip extends approximately parallel to said other 105 arm of the angular lever.

14 A circuit breaker as claimed in any preceding claim, wherein there are two of said contact springs spaced laterally apart and each carrying a respective movable con 110 tact at its free end and arranged to cooperate with an associated fixed contact, each said spring and its associated movable and fixed contacts constituting a single-pole circuit breaker unit; said latching lever and 115 detent abutment are disposed between said units; said latching lever comprises two bearing members located at its contact end, projecting laterally to respectively opposite sides thereof and each bearing against a 120 respective one of said contact springs; and said release device comprises two bimetal strips each associated with a respective breaker unit and each movable in a direction to move said detent abutment into its release 125 position upon occurrence of a current overload, and a release lever which is pivotal about an axis parallel to said rocker axis and having a lever arm provided with two mem1,592,139 bers projecting laterally to respectively opposite sides thereof, each said lever arm member being located in the path of movement of a respective one of said bimetal strips.

A circuit breaker as claimed in claim 19, wherein said housing comprises partition means dividing the interior of said housing into two laterally spaced breaker unit chambers each containing a respective one of said units, and a further chamber located between said breaker unit chambers, said latching lever and release lever being disposed in said further chamber.

16 A circuit breaker as claimed in claim 14 or 15, further comprising means defining two opposed, aligned enlongate slots extending in the direction in which said latching lever contact end is displaceable, and said bearing members of said latching lever are constituted by rod members whose ends engage in said elongate slots, whereby said elongate slots co-operate with said rod members to guide and limit the movement of said latching lever contact end.

I 7 A circuit breaker as claimed in claim 16, wherein said rod members are constituted by a shaft which passes through said latching lever contact end and extends parallel to the axis of said switching rocker.

18 A circuit breaker as claimed in claim 17, wherein said shaft is made of an electrical insulating material.

19 A circuit breaker as claimed in claim 16, 17 or 18, wherein said slots are formed in, and extend through, opposed lateral walls of said housing, and which further comprises two external, electrical insulating covering walls each covering a respective lateral housing wall provided with one said slot; a hollow shaft supporting, and providing a pivot bearing for, said switching rocker and passing through said housing; and a rivet passing through said covering walls, said lateral housing walls which are covered thereby and said hollow shaft for holding said covering walls to said housing and supporting said switching rocker, the axis of said rivet defining the pivot axis of the rocker.

A circuit breaker constructed and arranged to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.

J A KEMP & CO, Chartered Patent Agents, 14 South Square, Gray's Inn, London WC 1 R 5 EU.

Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon), Ltd -1981.

Published at The Patent Office, 25 Southampton Buildings, London, WC 2 A l AY, from which copies may be obtained.